We all know that Just The Board and the basic Next has parts missing such as the RTC and WIFI so I have started this topic to add part numbers to help people carry out the upgrades themselves if they wish to.
Also I have included the SRAM memory upgrade option for all versions of the Spectrum Next.

Memory upgrade:
The SRAM part numbers known to work so far are in blue. If anyone can confirm others please let me know.71V424S10Y(G) by Integrated Device Technology, Inc (IDT).
Other equivalents are:AS7C34096A-10JCN (10JIN) by Alliance Semiconductor Corp.K6R4008V1D-JC10 (JI10) by Samsung Electronics.
MCM6946YJ10 by Motorola, Inc.
CY7C1049CV33-10VC by Cypress Semiconductor corp.
IS61LV5128AL-10K(LI) by Integrated Silicon Solution, Inc (ISSI).
There are two slots available for the SRAM upgrade.
Instructions for fitting the extra SRAM can be found: here.

The rPI Zero W in theory should work but, is not tested by the team. It will need a recompile of the firmware so not for beginners. Note that the team have also stated the rPI0w Wifi is unlikely to be mainstream for the project as it has the WiFi module for that.